Manufacture of more dyeable regenerated cellulose filaments

ABSTRACT

Regenerated cellulose filaments of enhanced dyeability made by extruding and regenerating a viscose mixed with an aqueous solution of an aminoethyl cellulose containing at least 2 percent nitrogen.

United States Patent [72] lnventor Bryan A. Toms Leamington Spa, England 21 1 App]. No. 783,098

[22] Filed Dec. 11, 1968 [45] Patented Sept. 21, 1971 [73] Assignee Courtaulds Limited London, England [32] Priority Dec. 13, 1967 [33] Great Britain 54] MANUFACTURE OF MORE DYEABLE REGENERATED CELLULOSE FILAMENTS [50] Field of Search 106/164,

[56] References Cited UNITED STATES PATENTS 2,656,241 8/1953 Drake et al. 260/232 3,038,777 6/1962 Daul et a]. 8/1 16.4 3,305,377 2/1967 Mahomed 264/194 3,432,589 3/1969 Drisch 264/195 Primary Examiner.lulius Frome Assistant Examiner-James B. Lowe Attorney-Davis, Hoxie, Faithful] and Hapgood ABSTRACT: Regenerated cellulose filaments of enhanced dyeability made by extruding and regenerating a viscose mixed with an aqueous solution of an aminoethyl cellulose containing at least 2 percent nitrogen.

MANUFACTURE OF MORE DYEABLE REGENERATED CELLULOSE FILAMENTS This invention is concerned with a process for making regenerated cellulose filaments having a greater affinity for direct dyes and acid dyes.

It has already been proposed to manufacture regenerated cellulose filaments which may be dyed with acid dyes, by incorporating an aminosubstituted cellulose in the cellulose matrix of the filaments. The method involves fonning the xanthate of an aminoethyl cellulose containing between 1.2 and 1.6 percent of aminonitrogen, dissolving the xanthate in caustic soda solution to form a basified viscose, mixing the basified viscose with a normal viscose and spinning the mixture to obtain filaments of regenerated cellulose endowed with a sufficient basicity to render the filaments dyeable with acid dyes or more dyeable with direct dyes.

Attempts to xanthate a mixture of cellulose and an aminosubstituted cellulose in order to obtain in one process step a mixed viscose suitable for spinning,are frustrated by the different rates of xanthation of the kinds of cellulose. It has, hitherto, been necessary to accomplish the xanthation of each cellulosic species separately and to combine the xanthates in order to obtain the modified viscose. This has so complicated the process that more dyeable fibers are still not made on any substantial scale.

We have devised a simpler and cheaper process for making such filaments.

According to the present invention a process for making more dyeable regenerated cellulose filaments, comprises mixing an aqueous solution of an aminoethyl cellulose containing at least 2.0 percent by weight of amino nitrogen, with a viscose, and extruding the modified viscose through a multihole jet into a spin bath to form filaments.

The solubilites of aminoethyl cellulose in aqueous media are dependent on the amino content. Below approximately 2.0 percent nitrogen content the celluloses are not soluble per se in either aqueous sodium hydroxide or water, but require to be chemically modified, for example by conversion to xanthate, to acquire such a solubility. At about 2.0 percent nitrogen content the aminoethyl celluloses are appreciably soluble in aqueous caustic soda solution of percent by weight concentration. The solution may not be entirely clear at the lower limit of substitution, but the undissolved particles are gelatinous and lend only a slight turbidity or opalescence to the solution. As the nitrogen content is increased still further, the concentration of sodium hydroxide in the solvent may be decreased until ultimately, at approximately 4 percent nitrogen content and above, the aminoethyl celluloses are soluble in water. By selecting those aminoethyl celluloses which are soluble in aqueous caustic soda or water and thereby eliminating those which require xanthation to acquire such solubilities, the process of making more dyeable filaments is simplified and cheapened. We prefer that the nitrogen content of the aminoethyl cellulose should be from 2,7 to 3.3 percent by weight so that the ether is soluble in aqueous caustic soda and insoluble in water.

The water-soluble aminoethers containing 4 percent or more of nitrogen are liable to be leached from the regenerated cellulose filaments in which they are incorporated, particularly when the filaments are immersed in hot dilute acid solutions of the kind employed in wet-dyeing processes. However, this fault can be overcome by stretching the freshly coagulated filaments by at least 60 percent of their original length, or by cross-linking the filaments with any of the materials well known in the art of cross-linking cellulose, and particularly the permanently soluble cross-linking agents listed in US. Pat. No. 3,038,777 (British Pat. No. 950,073).

In the manufacture of aminoethyl cellulose by the reaction of cellulose with aminoethyl hydrogen sulfate and sodium hydroxide, it is not economically feasible to impart a nitrogen content of more than about 2.0 percent in one step, whilst preserving the cellulose against excesssive degradation, and it is probably this fact which has, hitherto, led workers in this field to propose the xanthation of aminoethyl celluloses, to

render them soluble and compatible with viscoses. We have found it possible to increase the nitrogen content to well above this figure by repeating the etherification reaction, that is reacting the aminoethyl cellulose and additional amounts of aminoethyl cellulose and additional amounts of aminoethyl hydrogen sulfate and sodium hydroxide, and have obtained thereby substituted celluloses all of which dissolve in aqueous sodium hydroxide and some in water.

The opalescent solutions of some aminoethyl celluloses formed in aqueous sodium hydroxide or water may be added to viscose without substantially affecting the filtration and spinning characteristics of that viscose, particularly if the mixing takes place some hours before the modified viscose is extruded. it is believed that the gelatinous particles causing the opalescence of the aqueous solutions are swollen cellulose segments or particles in a fit state for rapid xanthation and, therefore, solution, by reaction with excess carbon disulfide in the viscose or by transxanthation by contact with the viscose.

The criterion of whether the aminoethyl cellulose is sufficiently soluble in its aqueous sodium hydroxide solvent, is best decided, not in terms of the opalescence of the solution, but by mixing the solution with a viscose of the required composition and in the proportion required for the manufacture, and measuring filtration behavior of the viscose both before mixing and some time after, say up to 12 hours. If the filtration behavior is not intolerably different, the insoluble matter causing opalescence of the solution will not add significantly to the difi'rculties of spinning, if the modified viscose is significantly more difficult to filter, an aminoethyl cellulose having a higher difi'rcult to nitrogen content should be substituted for that under test.

In making the aminoethyl celluloses of this invention by separated reactions of the cellulose with successive amounts of aminoethyl hydrogen sulfate and sodium hydroxide, it is advisable to wash the byproduct impurities from the intermediate aminoethyl celluloses before adding more reagents, as this improves the efficiency of the next etherification reaction, but to leave the byproducts of the final reaction in the aminoethyl cellulose. The intermediate product, though it may be washed, should not be heated or dried, as this may lead to cross-linking and insolubilization. The final product may be dissolved immediately in the chosen solvent--sodium hydroxide or water.

We have found that regenerated cellulose filaments made by extruding the modified viscose, and containing at least 0.06 percent of nitrogen, may be dyed to a greater extent than those of unmodified regenerated cellulose with direct dyes and that similar filaments containing at least 0.25 percent of nitrogen may readily be dyed with acid dyes to an extent matching or surpassing wool.

The process of the present invention has several outstanding advantages. Firstly, because the aminoethyl celluloses having at least 2 percent by weight of nitrogen are soluble per se in the viscose, no additional amount of carbon disulfide is required to render the aminoethyl cellulose/viscose mixture homogeneous. Secondly the solution of the aminoethyl cellulose in aqueous caustic soda or in water is stable, unlike the solutions of xanthate derivatives of aminoethyl celluloses containing less than 2 percent nitrogen; they may therefore be made in substantial quantities and stored. The aqueous solutions may be injected into the viscose immediately before the mixture is extruded employing the technique established for the injection of pigments in the so-called spin-dyeing process. Thirdly, because the amino content of the substituted cellulose is so much greater than has been attempted hitherto, a smaller proportion of the aminoethyl cellulose suffices to obtain the required enhancement of dyeability.

The invention is illustrated by the following Examples in which percentages are by weight.

EXAMPLE 1 A viscose was made containing 7.95 percent of cellulose and 5.68 percent of sodium hydroxide and this was aged for 40 hours until the salt figure was about 6.0. There was then injected a solution containing 5.0 percent of soluble aminoethyl cellulose and 9.5 percent of sodium hydroxide at a rate of 143.6 grams of the solution per kilo of normal viscose. The percentage nitrogen in the solid soluble aminoethyl cellulose was 3.0 percent.

After injection, the material was spun immediately through a 300/5 jet into a spin bath of specific gravity 1.25 and temperature 42 C. containing 9.63 percent of sulfuric acid, 0.99 percent of zinc sulfate and 19.5 percent of sodium sulfate. The immersion length was 27 inches (68 cm.) and the material was given a 30 percent stretch. It was then treated (in skein form) with the following solutions:

cent, but decreased when the fiber was leached with 2 percent aqueous sulfuric acid at 95 C. for 1 hour.

The process was repeated with the freshly centrifuged fiber impregnated with a solution containing 3.5 percent formaldehyde, 3.5 percent magnesium chloride and squeezed to a liquid of 75 percent on the weight of the cellulose. Thereafter the fiber was dried at 180 F. and cured at 160 C. for 4 minutes. The nitrogen content of the fiber was again 0.25 percent and was not diminshed after the fiber had been immersed in 2 percent sulfuric acid for 1 hour.

EXAMPLE 4 The process of Example 3 was followed with the freshly coagulated filaments being stretched at draw ratio of 1.6:]. The finished filaments contained 0.28 percent by weight of nitrogen and even without cross-linking the cellulose, showed Total Number time Tempera- Fibre wash of washes (minutes) ture, 0. Constitution of bath 1 l 32 mls. concentrated sul- Acid pre washphuric acid per litre in soft water. 4 5 Demineralised water, pH 7. Do 2 5 (I) ifll'i i'w di 1 62 0 so um su sulphide bath' phide per litre, in soft 45 s t t t Sui hide wash 4 5 o wa er. Her-beach I 1 1g 32 m l s concentrated hydrosour bath I I chloi'ic acid per litre in 4 pderiinineriiised wtvstenH 7 4 5 8 em era ewaerp Final wash 2 5 48 Demineralised water with 0.1% sodium bicarbonate. Finish 1 15 Half neutralised oleic acid Bvg /h sodium hydroxide 1 Ambient.

The fiber was centrifuged for 5 minutes and dried at 80 C. After drying, the percentage nitrogen present on bone dried fiber was 0.28 percent. The exhaustion of a bath containing Azogeranine (0.2 gram per litre) was 55 percent compared with a 5.5 percent for a normal yarn spun under identical conditions, without the aminoethyl cellulose.

EXAMPLE 2 A viscose was prepared containing 9.l3 percent of sodium cellulose, 6.29 percent of sodium hydroxide having a salt figure of 6.6 and ball fall viscosity of 49 seconds at a temperature of l5 C. To this was added by injection 1.7 percent of aminoethyl cellulose based on the cellulose of the viscose as a 5.9 percent solution in 9.5 percent caustic soda solution. The solid aminoethyl cellulose made for the injector solution contained an average of 2.9 percent of nitrogen and had a range of 2.7 to 3.2 percent of nitrogen. The viscose was spun in a bath of 6.5 percent of sulfuric acid, 1.3 percent of zinc sulfate and 23.0 percent of sodium sulfate at 64 C. using a 7,500X4 jet and an immersion of 27 inches (68 cms.). The nitrogen value of the product after washing with solutions as in Example l was 0.06 percent. The staple fiber so produced was of 4% denier material and was highly crimped. It contained insufficient aminoethyl cellulose to make it significantly wool dyeing but there was sufficient of this additive to obtain enhanced direct dyeing characteristics. Thus, when dyed with Solephenyl Blue-Green it gave an exhaustion of 50 percent as compared with a fiber spun according to the same conditions, but without the aminoethyl cellulose addrtrve which gave an exhaustion of 15 percent.

EXAMPLE 3 no significant loss of nitrogen when leached with 2 percent sulfuric acid at C. for 1 hour.

What is claimed is:

1. In a process for making regenerated cellulose filaments by extruding viscose through a multiholed jet into an acid spin bath, the improvement which consists in mixing an aqueous solution of an aminoethyl cellulose containing at least 2 percent by weight of aminonitrogen with the viscose prior to extrusion, thereby enhancing the dyeability of said filaments.

2. A process as claimed in claim 1 in which the nitrogen content of the aminoethyl cellulose is between 2.3 and 3.7 percent by weight and the aminoethyl cellulose is dissolved in aqueous caustic soda.

3. A process as claimed in claim 1 in which the nitrogen content of the aminoethyl cellulose is at least 4 percent by weight and the aminoethyl cellulose is dissolved in water.

4. A process for making regenerated cellulose filaments of enhanced dyeability with direct dyes, as claimed in claim 1, in which the aminonitrogen content of the filaments is at least 0.06 p ercent by weight.

5. A process for making regenerated cellulose filaments of enhanced dyeability with acid dyes, as claimed in claim 1, in which the aminonitrogen content of the filaments is at least 0.25 percent by weight.

ifln a p rocess for making regenerated cellulose filaments by extruding viscose through a multiholed jet into an acid spin bath, the improvement which consists in mixing an aqueous solution of an aminoethyl cellulose containing 4 percent by weight nitrogen with the viscose prior to extrusion, thereby enhancing the dyeability of the filaments, and stretching the extruded filaments by at least 50 percent.

7. ln a process for making regenerated cellulose filaments by extruding viscose through a multiholed jet into an acid spin bath, the improvement which consists in mixing an aqueous solution of an aminoethyl cellulose containing at least 4 by weight nitrogen with the viscose prior to extrusion thereby enhancing the dyeability of the filaments, and reacting the extruded filaments with a cross-linking agent, for cellulose. 

2. A process as claimed in claim 1 in which the nitrogen content of the aminoethyl cellulose is between 2.3 and 3.7 percent by weight and the aminoethyl cellulose is dissolved in aqueous caustic soda.
 3. A process as claimed in claim 1 in which the nitrogen content of the aminoethyl cellulose is at least 4 percent by weight and the aminoethyl cellulose is dissolved in water.
 4. A process for making regenerated cellulose filaments of enhanced dyeability with direct dyes, as claimed in claim 1, in which the aminonitrogen content of the filaments is at least 0.06 percent by weight.
 5. A process for making regenerated cellulose filaments of enhanced dyeability with acid dyes, as claimed in claim 1, in which the aminonitrogen content of the filaments is at least 0.25 percent by weight.
 6. In a process for making regenerated cellulose filaments by extruding viscose through a multiholed jet into an acid spin bath, the improvement which consists in mixing an aqueous solution of an aminoethyl cellulose containing 4 percent by weight nitrogen with the viscose prior to extrusion, thereby enhancing the dyeability of the filaments, and stretching the extruded filaments by at least 50 percent.
 7. In a process for making regenerated cellulose filaments by extruding viscose through a multiholed jet into an acid spin bath, the improvement which consists in mixing an aqueous solution of an aminoethyl cellulose containing at least 4 by weight nitrogen with the viscose prior to extrusion thereby enhancing the dyeability of the filaments, and reacting the extruded filaments with a cross-linking agent, for cellulose. 